<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<div class='class_name'>test div tag.</div>
<script>
	window.onload = function(){
		var classObj = document.getElementsByClassName('div');
		// 打印CLASS名称
		alert(classObj.innerHTML);
	}

</script>
</body>
</html>